This invention relates to heat exchangers, and more particularly, to a straight tube heat exchanger with double wall tubes and leak detecting means.
In liquid metal fast breeder reactors, liquid sodium from the reactors passes through an intermediate heat exchanger and transfers heat to a closed liquid sodium loop. The liquid sodium passing through the reactor becomes radioactive; however, it is not sufficiently radioactive to cause the liquid sodium in the closed loop to become radioactive. The non-radioactive liquid sodium in the closed loop is passed through a steam generator to produce steam which drives a turbine and generator to make electricity. The steam generator thus becomes a vital link in the system. Since sodium and water or steam when mixed result in a high energy release, it is imperative that possibility of a leak, which would result in the mixing of the sodium and water or steam, be minimized. Single wall tube steam generators have been plagued with leaks and have not been successful in keeping primary and secondary fluids apart even though rigorous inspection techniques have been developed.